Tool Geometry Offset and Tool Wear Offset

Tool geometry offset and tool wear offset are possible to divide the tool offset to the tool geometry offset for compensating the tool shape or tool mounting position and the tool wear offset for compensating the tool nose wear. The tool geometry offset value and tool wear offset value can be set individually. When these values are not distinguished from each other, the total of the values is set as the tool offset value.

NOTE : Tool geometry offset and tool wear offset are optioned.

Let me show you if tool geometry offset and tool wear offset are distinguished from each other (picture left) and if they are not (picture right).

Tool Ofsett in CNC program

Usually, several tools are used for machining one workpiece. The tools have different tool length. It is very troublesome to change the program in accordance with the tools. Therefore, the length of each tool used should be measured in advance.

By setting the difference between the length of the standard tool and the length of each tool in the CNC machining can be performed without altering the program even when the tool is changed.

This function is called tool offset.

Program CNC configuration in CNC machine (part 2)

Reffer to the last post in program CNC configuration part 1 here
We will continue to program section configuration, a program section consist of several blocks. A program section starts with a program number and end with a program end code.

Program section configuration                                     Program section
Program number                                                              O0001;
Block 1                                                                           N1 G91 G00 X120.0 Y80.0;
Block 2                                                                           N2 G43 Z-32.0 H01;
Disable execution block                                                   / N3 G00 Z-200.0;
:

:
Block n                                                                           Nn Z0.0;
Program end                                                                   M30;

A block contains information that necessary for machining, such as a move command or coolant on/off command. Adding a slash ( / ) at the start of a block will disable the execution of some blocks.

A program number consisting of address O followed by a four–digit number is assigned to each program at the beginning registered in memory to identify the program.
In ISO code, the colon ( : ) can be used instead of O.
When no program number is specified at the start of a program, the sequence number (N....) at the start of the program is regarded as its program number. If a five–digit sequence number is used, the lower four digits are registered as a program number. If the lower four digits are all 0, the program number registered immediately before added to 1 is registered as a program number. Note, however, that N0 cannot be used
for a program number.
If there is no program number or sequence number at the start of a program, a program number must be specified using the MDI panel when the program is stored in memory

Program CNC configuration in CNC machine (part 1)

There are two types of program in cnc programming, there are main program and subprogram. Normally the CNC operates according to the main program. However, when a command calling a subprogram is encountered in the main program, control is passed to the subprogram. When a command specifiying a return to the main program is ecountered in a subprogram, control is returned to the main program.

The CNC memory can hold up to 400 main programs and subprograms.  A main program can be selected from the stored main programs to oprate the machine.
Usually the program consist of the followong component.

List of G Code in CNC programming

This is the list of G Code in CNC programming, also there is a group number and the function of the G code.

1. The modal G codes are placed in the states described below.

(1) The modal G codes are placed in the states marked with as indicated in Table 3.
(2) G20 and G21 remain unchanged when the clear state is set at power–up or reset.
(3) Which status G22 or G23 at power on is set by parameter G23 (No. 3402#7). However, G22 and G23 remain unchanged when the clear state is set at reset.
(4) The user can select G00 or G01 by setting bit 0 (G01) of parameter No. 3402.
(5) The user can select G90 or G91 by setting bit 3 (G91) of parameter No. 3402.
(6) The user can select G17, G18, or G19 by setting bit 1 (parameterG18) and bit 2 (parameter G19) of parameter No. 3402.

2.G codes other than G10 and G11 are one–shot G codes.

3.When a G code not listed in the G code list is specified, or a G code that has no corresponding option is specified, P/S alarm No. 010 is output.

4.Multiple G codes can be specified in the same block if each G code belongs to a different group. If multiple G codes that belong to the same group are specified in the same block, only the last G code specified is valid.

5.If a G code belonging to group 01 is specified in a canned cycle, the canned cycle is cancelled. This means that the same state set by specifying G80 is set. Note that the G codes in group 01 are not affected by a G code specifying a canned cycle.

6.G codes are indicated by group.

7.The group of G60 is switched according to the setting of the MDL bit (bit 0 of parameter 5431). (When the MDL bit is set to 0, the 00 group is selected. When the MDL bit is set to 1, the 01 group is selected.)

GENERAL FLOW OF OPERATING CNC MACHINE

When machining the part using the CNC machine tool, first prepare the program, then operate the CNC machine by using the program.

1) First, prepare the program from a part drawing to operate the CNC machine tool.
How to prepare the program is described in the Chapter PROGRAMMING.

2) The program is to be read into the CNC system. Then, mount the workpieces and tools on the machine, and operate the tools according to the programming. Finally, execute the machining actually.



How to operate the CNC system is described in the Chapter OPERATION.

Before the actual programming, make the machining plan for how to machine the part.
Machining plan
1. Determination of workpieces machining range
2. Method of mounting workpieces on the machine tool
3. Machining sequence in every machining process
4. Machining tools and machining
Decide the machining method in every machining process.

Tool coordinate system

If you want to create a CNC Program, you must know also about tool coordinate system.

dont forget to adjust the tools.

Coordinate system

There are easy ways to remember the coordinate system in programming Cnc.
1. Cartesian Coordinate Systems

2. Right hand rule

Information needed in CNC programming

There are information needed in CNC programming, such as :

1. Preparatory Information: units, incremental or absolute positioning

2. Coordinates: X,Y,Z, RX,RY,RZ

3. Machining Parameters: Feed rate and spindle speed

4. Coolant Control: On/Off, Flood, Mist

5. Tool Control: Tool and tool parameters

6. Cycle Functions: Type of action required

7. Miscellaneous Control: Spindle on/off, direction of rotation, stops for part movement

This information is conveyed to the machine through a set of instructions arranged in a desired sequence – Program